Abstract

Mammary and hepatic gene expression analysis in peripartal dairy cows using a bovine cDNA microarray 

J. J. Loor, H. M. Dann, R. E. Everts, S. L. Rodriguez-Zas, H. A. Lewin, and J. K. Drackley.  University of Illinois, Urbana.     

ADSA/ASAS/PSA Annual Joint Meeting, St. Louis, July 25-29, 2004

Simultaneous analysis of mammary and hepatic gene expression in peripartal dairy cows was studied using cDNA microarray technology.  Mammary and liver tissue were collected at –14, 1, and 14 d relative to parturition from two multiparous Holstein cows fed according to current NRC recommendations.  A microarray consisting of 7,872 cDNA inserts was used for transcript profiling.  Annotation was based on similarity searches using BLASTN and TBLASTX against human and mouse UniGene databases and the human genome.  Cy3- and Cy5-labelled cDNA from liver and a reference standard (derived from a mixture of cattle tissues) were used for hybridization (24 microarrays).  Loess-normalized log-transformed ratios (tissue/standard) were used to detect differential gene expression.  Benjamini and Hochberg’s False Discovery Rate (0.05) and a global gene error model, to account for the dependence of variation on signal intensities, were used to determine differential gene expression for the effect of tissue (1,040), day (20), and tissue by day (392) interactions.  Among genes with a significant tissue by day interaction, expression ratios greater than 5-fold in liver compared with mammary were found for 15, 12, and 13 genes on d –14, 1, and 14, respectively.  Among those showing tissue-specific expression, there were 26 genes with >5-fold expression in mammary compared with liver, and 44 genes with >5-fold expression in liver compared with mammary.  Expression patterns in liver clustered together on d –14 and 14, and in mammary on d 1 and 14.  Differences in expression patterns within these clusters ranged from 11% (liver) to 30% (mammary).  Results show the power of microarrays to dissect gene expression patterns in tissues during the peripartum period.  (Supported by award 2001-35206-10946 from NRI Competitive Grants Program/CSREES/USDA). Journal of Dairy Science, 87(Suppl. 1):T134.